a) Field of the Invention
The invention is directed to a device for handling disk-shaped objects in a handling plane of a local clean room containing a magazine seat which is adjustable vertically relative to the handling plane in a measurable manner and work stations for processing and inspection located substantially in the handling plane. Technical solutions of this kind are applied in the manufacture of integrated circuits, in particular for handling tasks.
b) Description of the Related Art
The increasing degree of integration and reduced design widths in the manufacture of integrated circuits lead to progressively stricter requirements for the quality of clean rooms. In order to meet such requirements, standardized transport containers, so-called standard mechanical interface boxes (SMIF boxes), are increasingly used to transport disk-shaped objects (wafers or masks) to individual processing stations, the cassette or magazine containing the objects in its shelves being fixed in a suitable manner to the base of these transport containers. When loading the processing machines, the magazines are removed from the transporting containers by appropriate means and the objects are taken out by a manipulator. After processing, the objects are returned to the shelves of the magazine and the magazine is replaced in the transport container.
The use of such SMIF boxes was previously restricted primarily only to large devices such as wafer steppers, implanters, etc., so that there is still no general application of such SMIF solutions to a great many process steps at the present time. Often, the magazines holding the objects are removed from the SMIF boxes by more or less complicated devices and transferred manually or automatically to the processing and inspection equipment
With the creation of device oriented, self-contained local clean rooms having a defined input/output interface, it has been possible to lower requirements for the surrounding clean room or to improve the quality of the environment of the objects in conventional clean rooms.
U.S. Pat. No. 4,746,256 describes a device for handling and inspecting wafers or masks as disk-shaped objects in a local clean room with SMIF boxes, manipulators and work stations. The manipulators and work stations are enclosed by a self-contained canopy in which the magazine, including the objects, can be introduced and seated after placing the SMIF boxes on the canopy. The manipulator is adjustable in the z axis for removing the objects from various planes of the magazine and for transferring them to the work station.
Further, it is known from U.S. Pat. No. 4,895,486 to determine the presence of wafer-like objects in a carder (magazine) and their position in the magazine relative to a reference plane by means of a monitoring device in that a first signal for the presence of such an object is coupled with a position signal. The first signal is obtained with the aid of an optoelectronic sensor monitoring the space in which the objects can be located. The second signal is generated by a position encoder coupled with a drive for raising and lowering the magazine. To determine the reference plane and the area in which the objects are seated, the space in the magazine is divided into vertical segments. In addition to a segment serving as reference plane and segments in which no wafer-like objects are found, window segments in which objects may be present are also defined. The magazine is indexed in that the locations of the window segments are determined by computer and stored therein based on information concerning the construction of the magazine used in the given case after detecting the reference plane in the magazine by measuring technique.
Although the solution described above can be used to determine the number of objects and their locations relative to a reference plane within the magazine, the magazine or manipulator must be positioned within the modular dimensions of the shelves of the magazine in order to remove the objects from the latter. Errors will occur if divergent magazine geometries and tolerances are not taken into account. This will result in problems when arbitrarily charging an empty magazine or when rearranging objects within a magazine or from one magazine to another as a preparatory or follow-up process to processing or inspection.